When Boston homicide detective James Doyle's partner is killed in an ambush, her dying words provide him with a clue that sends him to the remote island of Nantucket. There in the grey off-season when streets are empty, his hunt for the killer leads him to the heart of island where not even he can hide from the truth.

A Boston police officer goes to Nantucket to investigate the murder of his partner, but he finds more than he bargained for.